U.S. patent application number 13/764272 was filed with the patent office on 2013-06-13 for power on demand steering wheel angle sensor.
This patent application is currently assigned to Ford Global Technologies. The applicant listed for this patent is Ford Global Technologies. Invention is credited to Bradley G. Hochrein, Erick Michael Lavoie.
Application Number | 20130151080 13/764272 |
Document ID | / |
Family ID | 44316246 |
Filed Date | 2013-06-13 |
United States Patent
Application |
20130151080 |
Kind Code |
A1 |
Lavoie; Erick Michael ; et
al. |
June 13, 2013 |
POWER ON DEMAND STEERING WHEEL ANGLE SENSOR
Abstract
A system for powering a steering angle sensor coupled to a
steering wheel and a controller comprising a switch, coupled to the
sensor and the controller. The switch is activated upon motion of
the steering wheel or steering shaft. The switch, when activated,
connects a power supply, such as a vehicle battery, to the sensor
and the controller so that a new steering angle may be sensed and
stored. After a predetermined period of time, the controller sends
a signal to deactivate the switch and disconnect the power
supply.
Inventors: |
Lavoie; Erick Michael;
(Dearborn, MI) ; Hochrein; Bradley G.; (Dexter,
MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ford Global Technologies; |
Dearborn |
MI |
US |
|
|
Assignee: |
Ford Global Technologies
Dearborn
MI
|
Family ID: |
44316246 |
Appl. No.: |
13/764272 |
Filed: |
February 11, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12697307 |
Feb 1, 2010 |
8396628 |
|
|
13764272 |
|
|
|
|
Current U.S.
Class: |
701/42 |
Current CPC
Class: |
B62D 5/0481 20130101;
B62D 15/021 20130101; Y10T 74/20834 20150115 |
Class at
Publication: |
701/42 |
International
Class: |
B62D 5/04 20060101
B62D005/04 |
Claims
1. A system for powering a steering angle sensor during
ignition-off, the system comprising: a controller coupled to the
steering angle sensor; a switch coupled to the steering angle
sensor and the controller, the switch is activated by steering
wheel motion during times when an ignition switch is powered off;
and a power supply coupled to the switch and supplying power to the
steering angle sensor and the controller for a predetermined time
during times when the ignition switch is powered off such that,
upon steering wheel motion that activates the switch, a newly
sensed steering angle is stored in the controller.
2. The system as claimed in claim 1 wherein the controller sends a
signal to deactivate the switch after the predetermined period of
time has elapsed.
3. The system as claimed in claim 1 wherein the switch mechanism is
activated mechanically due to movement of the steering wheel
4. The system as claimed in claim 1 further comprising a motor
coupled to the controller, whereby the switch mechanism is
activated by receiving an electric pulse generated in the motor by
movement in the steering wheel.
5. The system as claimed in claim 1 further comprising a flag
indicating low battery power, the flag is stored in the controller
when there is insufficient battery power to detect and store a
change in steering angle and provides an indication that the
steering wheel angle must be relearned at key on.
6. The system as claimed in claim 4 wherein the motor is an
electric motor.
7. The system as claimed in claim 6 wherein the electric motor is
part of an electrically power assisted steering system.
Description
CROSS REFERENCE
[0001] This application is a divisional of co-pending U.S.
application Ser. No. 12/697,307 filed on Feb. 1, 2010, herein
incorporated by reference.
TECHNICAL FIELD
[0002] The inventive subject matter relates to a steering wheel
angle sensor and more particularly, to a power on demand steering
wheel angle sensor.
BACKGROUND
[0003] A steering angle sensor detects a steering angle of a
steering wheel of a vehicle and provides a signal necessary for a
vehicle control system to calculate a steering wheel angle, which
is used in many vehicle control systems. When the vehicle is not in
use, the ignition switch is powered off, and there is typically no
power provided to the steering angle sensor. In rare instances the
steering wheel may be turned when the vehicle is powered off, and
the many vehicle control systems that rely on a known steering
wheel angle will be affected, if a discrepancy exists between the
steering wheel angle at the time the vehicle is powered of and the
steering wheel angle at the time the vehicle is started up again,
vehicle control systems may be adversely affected. Examples of
vehicle systems that rely on accurate steering angle include
electronic stability control, roll stability control, electric
power steering, active park assist, advanced braking systems,
steerable headlamps, and advanced accident avoidance systems, among
others.
[0004] In order to combat this problem, a solution has been
provided in which continuous power is supplied to the steering
angle sensor, regardless of the state of the ignition switch.
Typically the continuous power is supplied by the vehicle's
battery, thereby consuming valuable battery power when the ignition
is turned off. Another proposed solution is to store as learned
angle at the time the vehicle is powered off and retrieve the
stored angle at power on. The stored angle is a tentative angle
until which time the vehicle moves and can confirm or reject the
stored angle as a correct steering angle. Still another solution
has been proposed in which power is intermittently supplied to the
steering angle sensor and the sensor periodically detects the
steering wheel angle. This solution conserves power but introduces
the likelihood that a change in the steering angle may be missed
should the change occur during a period of no power.
[0005] There is a need for a reliable solution to collecting a
steering angle even during periods when the vehicle is powered down
without wasting valuable battery power.
SUMMARY
[0006] The present invention is a power on-demand steering angle
sensor coupled to a steering wheel and a controller. A switch,
coupled to the sensor and the controller, is activated upon motion
of the steering wheel or steering shaft. The switch, when dosed,
connects a power supply. such as a vehicle battery to the sensor
and the controller so that a new steering angle may be sensed and
stored. After a predetermined period of time, the controller sends
a signal to open the switch and disconnect the power supply.
DESCRIPTION OF DRAWINGS
[0007] FIG. 1 is a view of an electrically assisted power steering
system having a power on demand steering angle sensor of the
present invention;
[0008] FIG. 2 is a block diagram of an embodiment of the
self-powered steering angle sensor of the present invention;
and
[0009] FIG. 3 is a block diagram of another embodiment of the
self-powered steering angle sensor of the present invention.
[0010] Elements and steps in the figures are illustrated for
simplicity and clarity and have not necessarily been rendered
according to any particular sequence. For example, steps that may
be performed concurrently or in different order are illustrated in
the figures to help improve understanding of embodiments of the
present invention.
DESCRIPTION OF INVENTION
[0011] While various aspects of the present invention are described
with reference to a particular illustrative embodiment, the
invention is not limited to such embodiments, and additional
modifications, applications, and embodiments may be implemented
without departing from the present invention. In the figures, like
reference numbers will be used to illustrate the same components.
Those skilled in the art will recognize that the various components
set forth herein may be altered without varying from the scope of
the inventive subject matter.
[0012] Referring to FIG. 1, an electrically assisted power steering
system 10 is shown that includes a steering wheel 12 attached to a
first end 14 of a steering shaft 16. A steering pinion gear 18,
attached to a second end 20 of the steering shaft 16 opposite the
first end 14, engages a steering rack gear 22 of a steering rack
24. Each end of the steering rack 24 includes a tie rod 26 attached
to a steerable wheel and tire assembly 28 in a conventional
manner.
[0013] A steering torque sensor 30 is incorporated in the steering
shaft 16 for detecting a steering torque applied by an operator to
the steering shaft 16 by way of the steering wheel 12. An electric
motor 32 includes an output gear 34 mounted on an output shaft 36
for drivingly engaging an assist input gear 38 mounted on the
steering shaft 16. Alternatively, not shown, the electric motor 32
may have its output shaft 36 and an output gear 34 arranged to
directly engage the steering rack 24.
[0014] The system may include a steering wheel angle sensor 40
connected to the steering shaft 16 and a vehicle speed sensor 42.
The steering wheel angle sensor 40 provides a steering angle signal
indicative of the relative rotational position of the steering
shaft 16. The various signals generated by the system are ted to an
electric motor control module 50, which then determines a motor
drive signal to actuate the electric motor 32, thereby providing
the desired assist torque.
[0015] At a point in time when the vehicle is powered off, the
steering angle sensed at ignition-off is stored in memory in the
controller 50. Any movement of the steering wheel 12 and steering
shaft 16 that occurs after power off will need to be sensed by the
steering angle sensor 40 and stored in memory in the controller 50
in order to provide an accurate steering angle for each vehicle
control system upon start up of the vehicle. Typically, when the
vehicle is powered off, there is no power supplied to the steering
angle sensor 40 or the controller 50. According to the present
invention, the power on demand steering angle sensor 40 includes a
switch mechanism 44 coupled to the sensor 40 and the controller 50
as well as a power supply 60. Physical movement of the steering
wheel 2 or steering shaft 16 affects the switch mechanism, which
becomes closed and thereby coupled to the power supply 60. The
power supply may be a battery, a generator, or other source of
power. The closed switch position allows power to be supplied to
the steering angle sensor 40 and the controller 50 so that the new
steering angle position may he detected and stored in memory.
[0016] In order to conserve battery power, the switch does not
remain in the dosed position. The switch connection occurs only for
a time period long enough in which to sense and store the new
steering angle. Within the controller 50, logic exists for the
switch to remain closed for a predetermined period of time, during
which the sensor 40 may sense the steering angle change and store a
new steering angle in a memory 52 of the controller 50. At the end
of the predetermined period of time, the switch 44 will be opened,
thereby de-coupling the power supply 60 from the steering angle
sensor 40. The battery power is only accessed as needed by the
steeling angle sensor 40.
[0017] The switch mechanism 44 may not require electric power in
order to close, however a signal from the controller is sent to the
switch 44 after the predetermined period of time has passed to
re-open the switch 44 disconnecting it from the power supply 68 and
conserving valuable battery power. In the embodiment shown in FIG.
2, the switch 44 is mechanically activated. The switch position is
affected by physical movement in the steering wheel 12 or steering
shaft 16. In another embodiment, shown in FIG. 3, the switch 44 is
activated electrically by a pulsee that ma be supplied by the
electric power assisted steering system motor 32. The pulse is
generated from movement associated with a change in the steering
angle while the vehicle is powered off. The electric motor 32 will
generate a small amount of power, i.e., a pulse, when the steering
shaft is moved, and that pulse may he used to selectively operate
the switch 44 in order to connect the power supply 60 to the
steering angle sensor 40 and the controller 50 for the
predetermined period of time.
[0018] As discussed above, the power supply 60 may be the vehicle's
battery. In the event there is insufficient battery power to update
the steering wheel angle according to the present invention, a "low
battery" flag may be stored in the controller 50 as an indicator
that a new steering wheel angle needs to he re-learned at key
on.
[0019] An advantage of the present invention is that less battery
power is consumed because power is supplied to the steering angle
sensor only when needed. Another advantage is realized in that the
absolute steering wheel angle, not to mention an accurate absolute
steering wheel angle, is available more of the time to various
vehicle control systems that require the steering wheel angle as an
input. A further advantage is realized in that a simple relative
angle measurement sensor may be implemented as an absolute sensor
once the steering angle is learned and would not require
re-learning the angle when the vehicle is keyed on and off. Because
a simple relative angle sensor is less expensive than an absolute
angle sensor, there is the benefit of a cost savings.
[0020] In the foregoing specification, the invention has been
described with reference to specific exemplary embodiments. Various
modifications and changes may be made, however, without departing
from the scope of the present invention as set forth in the claims.
The specification and figures are illustrative, rather than
restrictive, and modifications are intended to be included within
the scope of the present invention. Accordingly, the scope of the
invention should be determined by the claims and their legal
equivalents rather than by merely the examples described. For
example, the components or elements recited in any apparatus claims
may be assembled or otherwise operationally configured in a variety
of permutations and are accordingly not limited to the specific
configuration recited in the claims.
[0021] Benefits, other advantages and solutions to problems have
been described above with regard to particular embodiments;
however, any benefit, advantage, solution to problem or any element
that may cause any particular benefit, advantage or solution to
occur or to become more pronounced are not to be construed as
critical, required or essential features or components of any or
all the claims.
[0022] The terms "comprise", "comprises", "comprising", "having",
"including", "includes" or any variation thereof, are intended to
reference a non-exclusive inclusion, such that a process, method,
article, composition, or apparatus that comprises a list of
elements does not include only those elements recited, but may also
include other elements not expressly listed or inherent to such
process, method, article, composition or apparatus. Other
combinations or modifications of the above described structures,
arrangements, applications, proportions, elements, materials or
components used in the practice of the present invention, in
addition to those not specifically recited, may be varied or
otherwise particularly adapted to specific environments,
manufacturing specifications, design parameters or other operating
requirements without departing from the general principles of the
same.
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